Process for the production of beta gamma unsaturated ketones



Patented June 17, 1941 PROCESS FOR THEPRODUCTION OF BETA GAMlVIAUNSATURATED KETONES Franklin A. Bent, Berkeley, Calif., assignor toShell Development Company, San Francisco, Calif., a corporation 01'Delaware No Drawing. Original application December 27, 1937, Serial No.182,005, now Patent No. 2,197,462, dated April 16, 1940. Divided andthis application June 10, 1938, Serial No. 2. 2.979 Claims. (Cl. 260586)The present invention relates to a process for the production of betagamma unsaturated ke-' tones.

According to the present process, beta gm m a 1 1 unsaturated ketonesare prepared from alpha 5 V, 1 R5 bet-a unsaturated ketones byrearranging said alpha beta unsaturated ketones to the corre- E I lsponding beta gamma unsaturated ketones and 7' f" recovering the betagamma unsaturated ketones 5 JMQHL 12 substantially as fast as formed. 1S e By an alpha beta unsaturated ketone is meant l y a ketone containingan ethylene linkage attached I I s O to the carbonyl group. Theseketones contain a CH, O=Coo-Rt conjugated system of the structure I v H-1 om 0H: H Hi H:

B bt t tdkt t i ya eagammaunsaurae eoneismean w aketone containing anethylene linkage attached OER-(53H C to the carbonyl group through amethylene group. f R1 These ketones contain the structural grouping onon,

2 5 i I. H; 'H1,s I I? cm c'm 0 R5 c=o-oor r ll 1 l v -Q .1T9 F i cH,-cnr t -cH; V Rl 1 The alpha beta unsaturated ketones applicable CHPCH, 0R5 in the present process may be designated by the OH CH LI I R generalformula: a T1 f H O R CHr-C H Br R7 B J5? =(I'Jg( J-R 503', r R8 R4 I'M.x

' OKs-C1115": 5 (I) Rt wherein R1 through R1 may be any member ofcrime-0 oH- -o=o-o-$-m the group consisting of hydrogen, aliphatic and40 an -0455B: in I'M ,cyclo-paraffinic groups, with the provisions thatr I t p C and/or C be tertiary carbon atoms (s), and 1;, I a that thesum of the carbon atoms in R1, 2, and a 'bmlio C:HtC= -'-o --R be notless than two. These applicable alpha beta 6 r 27 H I. unsaturatedketones, it is seen, contain at least seven carbon atoms. Examples ofstructures con- F Rs taining simple R1, R2, and R3 radicals are:"j=tc-c- ER" 1 i CHnCl A t 1 V fi| Z RI CH 0- o-o- --R 5.0 ll

3* I I a C11Ha C== C C&-Rg

CzH5 R4 R1 5' I E: 4 1 R1 (IIIJRB J i g '7 :V (cm) o c= -o-ent ;n oteanlmayte connected with R1 or R3 t, by one or more methylene groups toform a poly methylene ring structure, for example, containing thegroupings,

Likewise, compounds in which Re is connected to R1 or R4 by one or moremethylene-groups are also applicable. Examples of" this structure are v1 separated from the reaction product by frac- These applicable alpha'betaunsaturated ketones, including their optical and stereo-isomers,constitute a class of unsaturated ketones difiering in several respectsfrofn'other unsaturated ketones. One notable characteristic of thesecompounds is the ease with which they may be alkylated. Unsaturatedketones of other structure, such as mesityl oxide:undecene-6-one-3, 3methyl cyclohexadienyl --2,6 acetone, etc., which are not alkylatedunder mild conditions are not applicable.

Unsaturated'ketones of the desired structure may be prepared by any oneof several known methods, the invention being independent of the mode offormation. One suitable method is through the condensation"of'ketonesfollowed by dehydration of the resulting ketolsh ,The reactions involvedin the synthesis are illustrated by the case of the formation of2,4,8-trimethylnonene-4-one-6 from methyl isobu'tylketone.

' o=CH -0.H+Hi0 C Alpha beta unsaturated ketone Any aliphatic,alicyclic, or aliphatic alicyclic ketone having a primary or secondaryalpha carbon atom, such as, for example, methyl ethyl ketone, methylisopropyl ketone, methyl cyclohexyl ketone, ethyl cyclopentylrketone,cyclohexanone, cyclopentanone, alpha methyl cyclopentanone, etc., may beemployed to'form the starting material of my process. Any suitablecatalyst such as CaCz, A1203,-.I IaQCzI:l5,,-POC;l3, H2504, HCI, HBr,HI, CaO, ThOz, ZnClz, Na,aluminum halide, organo magnesium halide,"sodium pyrosulfate, sodamide, triphenyl aluminurn etc, may be usedtoacce lerate tne reaction In most cases fthe -two reactionsproceedunderthe same conditions to the ketone, catalyst, and conditionsused. Thus, .-for examplawhen condensing methyl ethyl ketone with itself3-methyl heptene-3-one-5, 3,4-dimethyl hexene-3-one-5, 3,6,7-trimethylnonadiene-3,6-one-5, may be isolated. With A1203 as 'a' catalyst,forexample, B-methyl heptene-3-one- 5 is the predominant product, whilewith acid "nates. saturated trimer which is also applicable may becatalysts 3,4-dimethyl-hexene-3-one-5 predomi- The alpha beta, alphabeta doubly untionation, although this step is not necessary.

Another and convenient method for preparing the desired alpha betaunsaturated ketones is through .the condensation of a ketone of theabove-mentioned class with an alpha substituted aldehyde. Any aldehydehaving the structure wherein R and R represent aliphatic orcycloparaflinic groupsmay be employed. Thus, for example, methylpropaldehyde, ethyl propaldehyde, cycl'opentyl'propaldehyde are a few ofthe simpler 'aldehydes applicable.

Further, by usingtwo mols of aldehyde to one mol of ketone having ahydrogen atom attached to each of the alpha carbon atoms, an alpha beta,alpha beta doubly unsaturated ketone, which is likewise applicable, maybe made. For example, by reacting two mols of methyl butaldehyde withmethyl .ethyl'ketone and dehydrating,-one obtains H; CH: 11:

Another method of producing the desired alpha. beta unsaturated 'ketonesisthrough the dehydration of the corresponding acyloins. This may beaccomplished according to the scheme The tertiary carbon'atoms (C and/orC in the above-mentioned alpha beta unsaturated ketone structurecounteract to a certain extent the tendency of the unsaturated bonds toconju gate, i. e., to form static alpha'beta'unsaturated ketones. Thiscounteracting tendency manifests hydrolyze itself in the formation of.an equilibrium mixture of alpha beta and beta gammaunsatur'ated ketonein which the beta gamma ketone. content may range from traces to anappreciable'amount,

depending upon the size and character of' the radicals, R1, 2, 3, and-4.Although it usually'requires a considerable time forequi-librium to'become established under normal conditions, a few unsaturated ketonesof the above structure-equilibrate quite rapidly and, therefore, makethe preparation of the pure' alpha beta ketone dithcult. It is tobe'understood-ho'we'ver, that the formation of an equilibrium mixturecontaining some beta .gamma'ketone instead ofth'e pure alpha beta ketonedoes not detrimentallyaffect the applicability of these compounds in thepresent invention. r

By subjecting the alpha beta unsaturated ketone (or an equilibriummixture of alphabeta and beta gamma unsaturated ketone) to a fractionaldistillation at a rate not exceeding the rate of rearrangement, thelower boiling beta gamma unsaturated ketone may be'continually removedcausing the rearrangement to proceed to completion. This method ofproduci r'ig the desired beta gamma unsaturated ketone is quite simpleand generally applicable to 'the ketones of the above-mentionedstructure:

By simply fractionatmg in most cases the rearrangement takes place attoo slow a rate, even at elevated temperatures, to be economicallypractical. This may be remedied, however, by the use of a small amountof a substance which catalyzes the rearrangement, i. e., increases themobility of the system. It is found that alkali metal alkoxides inparticular, such as the various alcoholates of sodium, lithium,potassium, aluminum, magnesium, etc., are suited. Other catalysts, suchas alcoholic alkali and even mineral acid may sometimes be used.

Although the catalysts are usually effective in very small amounts, itis found that the rate of rearrangement is somewhat dependent upon theamount of catalyst present, being somewhat higher at catalystconcentration of about 3 to While the lower boiling alpha betaunsaturated ketones are conveniently rearranged at their normal boilingpoints, such high molecular weight unsaturated ketones as are unstableat their normal boiling points may be rearranged at a somewhat lowertemperature by carrying out the rearrangement under a suitablydiminished pressure.

The beta gamma unsaturated ketones, which, according to the presentinvention, are fractionated from the rearranging mixture substantiallyas fast as formed, differ from the alpha beta unsaturated ketones inseveral respects. They show essentially no exaltation of the molecularrefraction and have lower boiling points, melting points, refractiveindices, and densities. Furthermore, these compounds behave diiferentlyon being hydrogenated. In the hydrogenation of the alpha betaunsaturated ketones severe conditions are usually required and theyields are generally poor due to the simultaneous formation ofconsiderable amounts of hydrocarbons and saturated ketones. On the otherhand, the corresponding beta gamma unsaturated ketones undergohydrogenation under more favorable conditions and in a clean-cut mannerto yield the corresponding alcohols in excellent yields.

The freshly distilled beta gamma unsaturated ketones tend to-revert tothe equilibrium mixture upon being allowed to stand. Therefore, whenoperating with a system having a high mobility it is preferable toutilize the freshly preparedma- 'terialas-promptly as possible. Since,however, in the majority of cases, the rate of rearrangement at normaltemperatures and in the absence of a rearrangement catalyst isexceedingly slow, ample time for convenient execution is allowed.

"Thefollowing example illustrates the preparation of a beta gammaunsaturated ketone. by rearrangement of an alpha beta unsaturated ketoneaccording' to the process of the. present invention. a i V I Methylpropyl ketone is condensed with itself by refluxing-over calciumcarbide. The product consists of 'unreacted methyl propyl ketone and 4methyl-n'onene-4-one-6, with a small amount of isomeric alpha'betadimers and trimers. After distilling off the unreacted methyl propylketone, the condensation product are charged, along with about 1% ofsodium ethoxide, into a suitable fractionating apparatus. The mixture isbrought to boiling, held under total reflux for a few minutes, and thenfractionated while maintaining the stillhead tempertaure below theboiling point of the 4-methyl-nonene-4-one- (195.5 C; at 760 min). Inthe absence of a rearrangement catalyst; the fractionation will be veryslow. The distillate consists essentially of 4-methyl-nonene-3-one'-6.

Upon the completion of the rearrangement and removal of the ten carbonunsaturated ketones, the stillhead temperature may be allowed to rise tothe boiling point of the doubly unsaturated beta gamma, beta gammatrimer which may be collected separately. During this latter operationit is preferable to conduct the rearrangement and fractionation under adiminished pressure.

The present application is a division of my application Serial No.182,005, filed December '7, 1937 which issued as UIS. Patent 2,197,462on April 16, 1940.

I claim as my invention:

1. A process for the production of a beta gamma unsaturated ketone whichcomprises the step of heating an alpha beta unsaturated ketone andseparating the isomeric beta gamma unsaturated ketone from the reactionmixture at substantially the rate of formation from the alpha betaunsaturated ketone.

2. A process for the production of a beta gamma unsaturated ketone whichcomprises the steps of heating an alpha beta unsaturated ketone andfractionally distilling the isomeric beta gamma unsaturated ketone fromthe reaction mixture at a rate not exceeding the rate of formation fromthe alpha beta unsaturated ketone.

3. A process, for the production of a beta gamma unsaturated ketonewhich comprises the steps of heating an alpha beta unsaturated ketone inthe presence of an alcoholate of an alkali-forming metal and separatingthe isomeric beta gamma unsaturated ketone from the reaction mixture atsubstantially its rate of formation from the alpha beta unsaturatedketone.

44. A process for the production of a beta gamma unsaturated ketonewhich comprises the steps of heating an alpha beta unsaturated ketone inthe presence of from about 1% to 5% of an alcoholate of analkali-forming metal and separating the isomeric ,beta gamma unsaturatedketone from the rection mixture at substantially its rate of formationfrom the alpha beta unsaturated ketone.

5. A proces for the production of a beta gamma unsaturated ketone whichcomprises the steps of heating an alpha beta unsaturated ketone in thepresence of an alcoholate of an alkali-forming metal and removing thelowerboiling isomeric beta gamma unsaturated ketone by fractionaldistillation at substantially its rate of formation by a rearrangementreaction tending to establish an equilibrium mixture of alpha beta andbeta gamma unsaturated ketones.

6. A process for the production of a beta gamma unsaturated ketone whichcomprises the steps of heating an alpha beta unsaturated ketone at atemperature not substantially greater than the normal boilingtemperature and separating the isomeric beta gamma unsaturated ketonefrom the reaction mixture at substantially the rate of formation fromthe alpha beta unsaturated ketone.

7. A process for the production of a beta gamma unsaturated ketone whichcomprises the steps of heating an alpha beta unsaturated ketone at atemperature not substantially greater than the normal boilingtemperature in the presence of an alcoholate of an alkali-forming metaland fractionally distilling the isomeric beta gamma unsaturated ketonefrom the reaction mixture at substantially the rate of formation fromthe alpha beta unsaturated ketone.

8. A process for the production of a beta gamma unsaturated ketone whichcomprises the steps of heating an alpha beta unsaturated ketone atsubstantially the boiling temperature under diminished pressure in thepresence of an alcoholate of an alkali-forming metal and fractionallydistilling the isomeric beta gamma unsaturated ketone from the reactionmixture at substantially the rate of formation from the alpha betaunsaturated ketone.

9. A process for the production of a beta gamma unsaturated ketone whichcomprises heating an alpha beta unsaturated ketone in the presence of arearrangement catalyst, and separating the isomeric beta gammaunsaturated ketone from the reaction mixture at substantially its rateof formation therein.

10. A process for the production of a beta gamma unsaturated ketonewhich comprises heating an alpha beta unsaturated ketone in the presenceiof a rearrangement catalyst of the group consisting of the alcoholatesof the alkaliforming metals and the alcoholic alkali solutions, andseparating the isomeric beta gamma unsaturated ketone from the reactionmixture at substantially its rate of formation therein.

FRANKLIN A. BENT.

